This invention relates to an apparatus and method for disinfecting and sterilizing, and relates more particularly to an apparatus and method with filtering means for providing sterile infusion fluid.
In general, patients who require certain medications, re-hydration, blood replenishment, nutritional supplements, and the like, receive appropriate sterile fluids by infusion directly into the patient""s bloodstream. This is typically accomplished through use of an intravenous (IV) bag connected via a plastic tubing to a needle with is inserted into a patient""s vein or artery. IV bags usually provide from one to two liters of sterile fluid before their supply is spent, after which a new IV bag must be provided. Changing IV bags can be a time-consuming process. Thus, IV infusion may work well for slow infusion rate and/or small volume procedures. However for certain procedures which require large volumes and/or rapid supplies of fluid, such as providing replacement fluid for hemofiltration and providing transfer fluid for peritoneal dialysis, infusion using IV bags is not desirable.
Instead, with hemofiltration, non-sterile fluid is filtered through one or a series of filtering devices and then infused directly into the patient""s bloodstream. The filtered fluid may be a patient ultrafiltrate or a non-sterile substitution fluid received from an outside source, so as to minimize a patient""s fluid loss. In any event, to accomplish filtration with minimal risk to the patient, the filter arrangement used in the process must remove endotoxins, bacteria and other pyrogen-inducing compounds. If a filter should fail during the process, a patient may suffer a septic or pyrogenic reaction due to inadequately filtered fluid.
Several filtration techniques and devices currently exist for hemofiltration and dialysis. Online production of substitution fluid is described, for example, in D. Limido et al., xe2x80x9cClinical Evaluation of AK-100 ULTRA for Predilution HF with On-Line Prepared Bicarbonate Substitution Fluid. Comparison with HD and Acetate Postdilution HFxe2x80x9d, International Journal of Artificial Organs, Vol. 20, No.3 (1997), pp. 153-157. Hemodiafiltration schemes using a single dialyzer cartridge containing a high flux semi-permeable membrane are described in P. Ahrenholz et al., xe2x80x9cOn-Line Hemodiafiltration with Pre- and Postdilution: A comparison of Efficiencyxe2x80x9d, International Journal of Artificial Organs, Vol. 20, No.2 (1997), pp 81-90 (xe2x80x9cAhrenholz et al.xe2x80x9d). A hemodiafiltration scheme using first and second dialyzer cartridges is described in J. H. Miller et al., xe2x80x9cTechnical Aspects of High-Flux Hemodiafiltration for Adequate Short (Under 2 Hours) Treatmentxe2x80x9d, Transactions of American Society of Artificial Internal Organs (1984), pp. 377-380.
These and other prior art schemes for online filtration ultimately rely on a single filter as the final barrier between contaminated and sterile fluid supplies for infusion. A failure in this final barrier could be fatal or life-threatening. A particular danger lies in dialyzer schemes which rely on back-filtration of blood, since some pyrogen-inducing substances containing endotoxin fragments have been shown to pass through the single filter during the procedure. See, for example, R. Bigazzi, et al., xe2x80x9cHigh-Permeable Membranes and Hypersensitivity-like Reactions: Role of Dialysis Fluid Contaminationxe2x80x9d, Blood Purification, Vol. 8, No. 4 (1990), pp. 190-198 and N. Hosoya, et al., xe2x80x9cBack Diffusion Rather than Back Filtration Enhances Endotoxin Transport Through Highly Permeable Dialysis Membranesxe2x80x9d, ASAIO Transactions, Vol 36, No. 3 (1990), pp. M311-313.
Therefore, there is a need to provide a redundant, stand-alone sterile fluid filter that can be used with any machine or method that produces phyisiologic fluid, preferably in large volumes, which is suitable for patient infusion. There is a further need for a stand-alone filter that can be used with large volume and/or rapid flow procedures.
In order to address the shortcomings of the prior art, a first embodiment of the instant invention includes a filtration assembly comprising: (1) a first sterilization stage including an inlet port for receiving a fluid into the filtration assembly, the first sterilization stage further including at least one first stage outlet; (2) a second sterilization stage including an outlet port for expelling the fluid from the filtration assembly after filtration, the second sterilization stage having at least one second stage inlet; and (3) a stage connector fixedly attached between the first and second stages and allowing communication of the fluid between the first stage outlet and the second stage inlet.
A second embodiment of the instant invention includes a method for filtering a fluid comprising the steps of: (1) receiving a fluid at an inlet port of a casing; (2) transporting the fluid to a first filter within the casing; (3) filtering the fluid through an outer portion of the first filter; (4) expelling the fluid through an end of the first filter to an interstage connector; (5) receiving the fluid from the interstage connector at an end of a second filter; (6) filtering the fluid from the end of the second filter to an outer portion of the second filter; (7) expelling the fluid from the outer portion of the second filter; and (8) receiving the fluid at an outlet port for infusion to a patient.
A third embodiment of the instant invention includes a filtration assembly comprising: (1) a casing; (2) a separating rib for dividing the casing into a first portion for enclosing a first filter and a second portion for enclosing a second filter, the separating rib further for preventing direct fluid communication between the first and second portions; (3) an inlet port in fluid communication with the first filter; (4) an outlet port in fluid communication with the second filter; and (5) at least one interstage portion for providing fluid communication between an end of the first filter and an end of the second filter.
It is contemplated that the dual filtration assembly of the present invention may be manufactured in sections, each comprising a separate casing for later attachment. It is further contemplated that the dual filtration assembly may be manufactured such that both casings are provided simultaneously. It is additionally contemplated that a single, large casing may be provided with separate filtration compartments for accomplishing redundant filtration.
An advantage of the instant invention is that a redundant filtration system for producing infusate for a patient is provided in which the chance of septic and/or pyrogenic reactions occurring due to a failure of one filter is decreased. Systems of the prior art do not provide for such redundant protection.